It is common in well sites to have well conduits carrying fluids such as oil and gas from the well to a storage tank, pipeline, or the like. In the very cold weather that is commonly encountered in northern areas, viscosity of the fluid increases, and can inhibit or block flow in these well conduits. It is not uncommon to close down wells in the winter because of these flow problems. Such closure is costly and undesirable, especially when petroleum prices are relatively high, as is often the case in the winter when demand for heat is greater.
Prior art directed to maintaining flow in such well conduits has commonly provided an electric heat tape or a heating conduit that is placed along side the well conduit and covered with insulation such that heat is transferred to the well conduit to raise the temperature and maintain flow therein. Where an electrical grid is not available, a major obstacle to this method has been sufficiently heating and circulating warm fluid in such a heating conduit.
A typical well site will include a small internal combustion engine operating a pump jack or other well pump mechanism to raise petroleum fluid from a subterranean reservoir. Where an electrical grid is available, an electric motor can be used, however the internal combustion engine is widely used and can be fuelled from natural gas coming out of the well, propane, or other fuel. Engines typically comprise a crankshaft with a large flywheel attached on one end and a pulley wheel is attached to the opposite end, and a clutch is provided outboard of the pulley wheel on the end of the crankshaft to control rotation of an output shaft driving the well pump.
The flywheel and pulley wheel rotate whenever the engine is running. The output shaft rotates to drive the well pump when the clutch is engaged, and stops rotating when the clutch is disengaged so that the well pump can be stopped while the engine is left running. Typically as well, the internal combustion engine is started with a hand crank that engages the flywheel end of the crankshaft.
It is known to tap into the liquid coolant circuits on such engines, and incorporate the heating conduit into the coolant circuit such that the coolant fluid circulates through the heating conduit and coolant circuit.
When temperatures drop to a point where flow becomes a problem however, the small engines typically in use do not provide enough heat to maintain the temperature of the coolant sufficiently high to warm the fluid lines. As well the operating temperature of the engine is lowered below its preferred level by the extra cooling resulting in less than optimum engine performance.
A typical well site will require a heating conduit from 200 to 300 feet long, requiring a pump with sufficient capacity to circulate the engine coolant through the lengthy conduit. Engines typically in use often have no coolant pump, or a very low capacity coolant pump, and so a circulating pump has been added in the prior art apparatus for circulating the coolant through the heating conduit.
Because the flywheel end of the crankshaft must be kept clear so that the hand crank can engage that end of the crankshaft to start the engine, in the prior art the circulating pump has been driven from other locations. The circulating pump has typically been driven from the clutched output shaft driving the well pump, and so the circulating pump stops when the well pump is stopped for service or the like. When the circulating pump stops, the coolant flow through the heating conduit stops. Alternatively the circulating pump has been driven with the fan belt of the engine off the pulley wheel, however the fan belt and drive on such engines is quite lightly built, and such a pump drive has been subject to breakdown.
Although not common, where it is critical that flow be maintained and the significant costs are warranted, it is also known to provide another separate internal combustion engine having a liquid coolant circuit and then incorporating the heating conduit into that coolant circuit such that the coolant fluid flows through the heating conduit and coolant circuit. The separate engine is chosen to have a heat output sufficient to maintain the coolant in the coolant circuit and heating conduit at the necessary temperature. The coolant pump of the separate engine can have a coolant pump capacity sufficient to circulate the coolant through the heating conduit, or could drive a separate booster pump. The separate engine thus has the sole purpose of heating the well conduits.